The reaction mechanism of the Na-K pump of the red blood cell will be investigated. The effects of ions at the inner and outer surface of the pump and of metabolites at the inner surface of the pump on the pump rate will be determined and from the results of such studies conclusions about the pump mechanism will be drawn. First, we will continue to determine the characteristics of pump inhibition by vanadate. By determining whether vanadate is a competitive, non-competitive or uncompetitive inhibitor with respect to inside Na, outside K, inside K and outside Na it should be possible to come to some conclusions about the Na pump reaction mechanism. We will continue our investigation of the mechanism by which internal K increases the pump rate. We will focus our attention on the possibility that internal K increases the concentration of ATP and decreases the concentration of ADP perhaps by increasing the activity of one of the glycolytic enzymes. Finally, we will perform experiments to explore the interaction of Mg with the Na pump and to determine how Mg competes with inhibition by oligomycin and promotes inhibition by vanadate.